In recent years, the use of ultrasound systems for medical diagnostics has continued to grow. Ultrasonic systems are used in a vast array of medical fields and diagnostic areas. As the desire to use ultrasonic imaging systems has grown, so has the level of sophistication of those systems.
To assist physicians and staff in performing diagnostic and therapeutic procedures, a number of ultrasonic imaging systems have been designed for use with catheters. In general, these systems comprise a single transducer element, frequently made of piezoelectric material, attached to the distal portion of an imaging catheter. The imaging catheter is inserted into the patient so that the transducer is positioned to image a desired region of the patient's anatomy.
Such catheters typically operate by sending an electrical signal or excitation pulse to the transducer. The transducer then converts the electrical energy into mechanical energy, which propagates into a patient's surrounding body tissues as ultrasonic waves. The frequency of the emitted ultrasonic waves are a function of the resonant frequency of the transducer element and the frequency content of the excitation pulse. The ultrasonic waves are reflected back to the transducer as reflected signals or echoes, which the transducer converts into an electrical signal, which is used to produce an image of the patient's anatomy.
By operating with a transducer having only one resonant frequency, however, the focusing capability of the imaging catheters is limited. The frequency of emitted sound waves is a function of the resonant frequency and bandwidth of the transducer element and the frequency content of the excitation pulse, and can only be altered by varying the excitation pulse frequency. As a result, the ability of the single resonant frequency transducer element to be focused at different depths into the surrounding tissue is limited.
Other catheter systems attempt to solve the focusing problem by switching out the catheter or imaging core during operation so that the replacement catheter would contain a transducer element with a different frequency. However, this method of catheter replacement is very time-consuming which necessarily makes the imaging procedure longer than is necessary.
Therefore, there exists a present need to provide a multiple resonant frequency transducer for an imaging catheter system, which is capable of providing high quality ultrasound images at different depths without having to switch out the catheter or the imaging core.